Sulfited fats

ABSTRACT

Sulfited fats prepared by oxidation of fats with oxygen-containing gas mixtures and simultaneous or subsequent sulfitation using alkali and/or ammonium hydrogen sulfites, wherein the fats used are mixtures containing 
     (A) fats having iodine numbers below about 100 and 
     (B) fatty acid esters having iodine numbers of from about 60 to about 100 and containing from 12 to 24 carbon atoms in the linear or branched, natural and/or synthetic fatty acid residue and from 1 to 5 carbon atoms in the monofunctional alcohol residue, 
     the ratio by weight of (A) to (B) being from about 9:1 to about 1:4.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to sulfited fats prepared from difficultlysulfitable fats having iodine numbers below 100, to their use as oilingagents for leather as skins and to a process for sulfiting fats havingiodine numbers below 100.

2. Statement of Related Art

Sulfited fats used as oiling agents for leather and skins are producedby oxidation of fats with oxygen-containing gas mixtures, for exampleair, and simultaneous or subsequent sulfitation with alkali and/orammonium hydrogen sulfite. For fats to be sulfited at all, it isabsolutely essential to oxidize them before or during sulfitation byintroduction of oxygen-containing gas mixtures. However, since theoxidizability of fats decreases with decreasing iodine number,relatively highly unsaturated fats and oils, i.e. those having iodinenumbers above about 100 and preferably above about 130, are normallyused (cf. for example "Rauchwarenherstellung und Pelzkonfektion", VEBFachbuchverlag Leipzig 1970, page 116).

Sulfited fats prepared from sea-animal oils having high iodine numbers,for example whale oil or fish oil, or from vegetable oils having highiodine numbers, for example soya oil, form readily water-emulsifiablesubstances of high emulsion stability which are particularly suitablefor oiling leather and skins. If, by contrast, difficultly sulfitablefats having an iodine number below 100, for example sperm oil, aresubjected to oxidizing sulfitation, the oxidation velocity of the fatsdecreases drastically and products difficult to emulsify in water andhaving poor emulsion stability are obtained. In order nevertheless to beable to use these sulfitation products for oiling leather and skins,they have to be mixed with emulsifiers or with water-emulsifiable fatswhich are capable of co-emulsifying the difficultly emulsifiablesulfitation products.

STATEMENT OF THE INVENTION

Other than in the operating examples, or where otherwise indicated, allnumbers expressing quantities of ingredients or reaction conditions usedherein are to be understood as modified in all instances by the term"about".

An object of the present invention is to provide sulfited fats preparedfrom difficultly sulfitable fats having iodine numbers below 100 whichform readily water-emulsifiable products of high emulsion stability andwhich are suitable for oiling leather and skins.

It has now surprisingly been found that difficultly sulfitable fatshaving iodine numbers below 100, for example coconut oil, palm kerneloil, palm oil, tallow, lard, neat's-foot oil, sperm oil, whale oil,triolein, oleic acid, wax esters, fatty acid monoglycerides, fatty aciddiglycerides, and/or fatty acid triglycerides, form readilywater-emulsifiable sulfitation products of high emulsion stabilityproviding they are mixed before the oxidizing sulfitation step withfatty acid esters having iodine numbers of from 60 to 100 in a ratio byweight of fat to ester of from 9:1 to 1:4. Suitable fatty acid esterscontain from 12 to 24 carbon atoms in the fatty acid residue, which isof natural and/or synthetic origin and which may be linear or branched,and from 1 to 5 carbon atoms in the monofunctional alcohol residue.Fatty acid esters containing unsaturated fatty acid residues can be useseither individually or in combination with fatty acid esters containingsaturated fatty acid residues.

Accordingly, the present invention relates to sulfited fats prepared byoxidation of fats with oxygen-containing gas mixtures and simultaneousor subsequent sulfitation using alkali and/or ammonium hydrogensulfites, wherein the fats used are mixtures containing

(A) fats having iodine numbers below about 100, and

(B) fatty acid esters having iodine numbers from 60 to 100 andcontaining from 12 to 24 carbon atoms in the linear or branched, naturaland/or synthetic fatty acid residue and from 1 to 5 carbon atoms in themonofunctional alcohol residue;

the ratio of weight of A to B being from 9:1 to 1:4.

Difficultly sulfitable fats having iodine numbers below 100, andpreferably of from 7 to 95, are preferably mixed with fatty acid estershaving iodine numbers of from 60 to 100 in a ratio by weight of fat tofatty acid ester of from 4:1 to 2:3.

The difficultly sulfitable fats having iodine numbers below 100 include,for example, fats and oils containing unsaturated fatty acids and/orfatty acid esters, natural and/or synthetic unsaturated fatty acidscontaining from 12 to 24 carbon atoms, if desired in combination withnatural and/or synthetic saturated fatty acids containing from 12 to 24cabon atoms, natural and/or synthetic unsaturated fatty acid esterscontaining from 12 to 24 carbon atoms both in the fatty acid residue andin the alcohol residue, if desired in combination with the analogousnatural and/or synthetic saturated fatty acid esters, synthetic fattyacid monoglycerides prepared from unsaturated fatty acids containingfrom 12 to 24 carbon atoms, if desired in combination with the analogoussaturated, synthetic fatty acid monoglycerides, synthetic fatty aciddiglycerides and triglycerides prepared from unsaturated orunsaturated/saturated fatty acids containing from 12 to 24 carbon atomsand mixtures of fats from the above-mentioned groups. The preferreddifficultly sulfitable fats having iodine numbers below 100 andpreferably of from 7 to 95 include coconut oil, palm kernel oil, palmoil, tallow, lard, neat's-foot oil, sperm oil, whale oil, triolein.oleic acid, wax exters, fatty acid monoglycerides, fatty aciddiglycerides, fatty acid triglycerides, and mixtures thereof.

The difficultly sulfitable fats having iodine numbers below 100 andpreferably of from 7 to 95 are preferably mixed with fatty acid estershaving iodine numbers of from 70 to 85. It is possible to use bothunsaturated fatty acid esters and also mixtures of unsaturated andsaturated fatty acid esters having iodine numbers of from 60 to 100 andpreferably of from 70 to 85.

Suitable fatty acid esters having iodine numbers of from 60 to 100 andpreferably of from 70 to 85 contain from 12 to 24, preferably from 12 to18, and more preferably from 16 to 18 carbon atoms in the fatty acidresidue and from 1 to 5 carbon atoms in the monofunctional alcoholresidue. The fatty acid residue may be linear or branched. Fatty acidmethyl, ethyl, isopropyl, and/or isobutyl esters are preferably used asthe fatty acid esters.

Fat mixtures containing difficultly sulfitable fats having iodinenumbers below 100 and preferably of from 7 to 95, and fatty acid estershaving iodine numbers of from 60 to 100, and preferably of from 70 to85, are sulfited with 0.5 to 2.5 moles of alkali and/or ammoniumhydrogen sulfites or alkali and/or ammonium hydrogen sulfites and alkaliand/or ammonium sulfites in the form of aqueous solutions orsuspensions, preferably in the form of saturated aqueous solutions, attemperatures of from 70° to 110° C., and preferably at temperatures offrom 85° to 95° C.

The present invention also relates to the use of the sulfited fatsaccording to the invention, if desired in combination with other oilingagents known per se and/or with anionic and/or nonionic emulsifiers, asoiling agents for leather and skins.

Suitable oiling agents which may be used together with the sulfited fatsaccording to the invention are, for example, sulfated fats, sulfonatedfats, sulfited fats prepared from high-iodine fats, sulfochlorinatedfats or phosphated fats, neutral oils, and mixtures thereof.

Suitable anionic and/or nonionic emulsifiers are, for example, alkyleneoxide adducts of fatty alcohols, fatty acids, fatty acid amides, fattyamines, and/or alkyl phenols and sulfuric acid and/or phosphoric acidesters thereof, fatty alcohol sulfates, alkyl sulfates and/oralkylbenzene sulfonates.

Oiling agents containing sulfited fats according to the invention areused in quantities of from 1 to 20% by weight, based on the pelt orsharing weight, and preferably in quantity of from 1 to 2% by weightduring chrome tanning, and in quantities of from 4 to 16% by weightduring the main tanning process or, depending on the type of leather orskin, in concentrations, of from 2 to 10 g/l liquor and preferably inconcentrations of from 5 to 7 g/l liquor. In oiling agents consisting ofseveral oiling agents and, optionally, emulsifiers, the sulfited fatsaccording to the invention are present in a quantity of from 10 to 95%by weight.

The oiling temperature is in the range of from 20° to 75° C. andpreferably in the range of from 35° to 50° C.

The present invention also relates to a process for sulfiting fatshaving iodine numbers below about 100, characterized in that (A) fatshaving iodine numbers below about 100 are mixed with (B) fatty acidesters having iodine numbers of from about 60 to about 100 andcontaining from 12 to 24 carbon atoms in the linear or branched, naturaland/or synthetic fatty acid residue and from 1 to 5 carbon atoms in themonofunctional alcohol residue, the ratio by eight of (A) to (B) beingfrom about 9:1 to about 1:4, and the resulting fatty mixtures areoxidized in known manner with oxygen-containing gas mixtures and thensulfited using alkali and/or ammonium hydrogen sulfites, if desiredwhile more oxygen-containing gas mixture is passed through.

It is preferred to use sulfite fat mixtures containing fats havingiodine numbers below about 100 and preferably of from 7 to 95 and fattyacid esters having iodine numbers of from 60 to 100 in a ratio by weightof from 4:1 to 2:3.

The difficultly sulfitable fats having iodine numbers below 100, whichare suitable as adducts for the process according to the invention forsulfiting fats having iodine numbers below 100, are those describedabove.

According to the invention, the difficultly sulfitable fats havingiodine numbers below 100 and preferably of from 7 to 95 are mixed beforethe oxidizing sulfitation with fatty acid esters having iodine numbersof from 60 to 100 and preferably of from 70 to 85 in a ratio by weightof fat to fatty acid ester of from 9:1 to 1:4 and preferably of from 4:1to 2:3. Suitable fatty acid esters having iodine numbers of from 60 to100 and preferably of form 70 to 85 contain from 12 to 24, preferablyfrom 12 to 18 and more preferably from 16 to 18 carbon atoms in thefatty acid residue and from 1 to 5 carbon atoms in the monofunctionalalcohol residue. The fatty acid residue may be linear or branched. It ispossible to use both unsaturated fatty acid esters and also mixtures ofsaturated and unsaturated fatty acid esters. The fatty acid esters canbe prepared by various methods, for example by transesterification offats and oils with monofunctional alcohols containing from 1 to 5 carbonatoms or by esterification of fatty acids of natural and/or syntheticorigin with monofunctional alcohols containing from 1 to 5 carbon atoms.Methanol, ethanol, isopropanol and/or isobutanol are preferably used asalcohol components for the preparation of fatty acid esters.

In the process of the invention for sulfiting fats having iodine numbersbelow 100, the fat mixtures are oxidized at 70° to 200° C., andpreferably at 80° to 120° C. by passing an oxygen-containing fatmixtures through the fats, which are then sulfited, optionally whilemore oxygen-containing gas mixture is passed through, at 70° to 110° C.and preferably at 85° to 95° C. with 0.5 to 2.5 moles of alkali and/orammonium hydrogen sulfites or alkali and/or ammonium hydrogen sulfitesand alkali and/or ammonium sulfites/kg fat mixture used in the form ofan aqueous solution or suspension, preferably in the form of a saturatedaqueous solution. Sulfitation is preferably carried out with 0.5 to 2moles alkali and/or ammonium hydrogen sulfites or in admixture withalkali and/or ammonium sulfites/kg fat mixture used.

The sulfiting agents are mixed with the oxidized at mixtures by addingthe sulfiting agent in the form of an aqueous solution or suspension andpreferably in the form of a saturated aqueous solution to the oxidizedfat mixture or by stirring and oxidized fat mixture into an aqueoussolution or suspension and preferably into a saturated aqueous solutionof the sulfiting agent.

The sulfited fats according to the invention are distinguished by highwater emulsifiability with excellent emulsion stability. They aretherefore particularly suitable for oiling leather and skins.

Compared with sulfitation products prepared from high-iodine fats, forexample fish oil, the sulfitation products according to the inventionshow distinctly better light stability. Thus, the light fastness ofleathers, as measured in accordance with DIN 54 004, oiled with fish oilsulfite reaches stage 1 of the 8-stage cotton blue scale while leatherstreated with the sulfited fats according to the invention reach stage 4or stage 5. On the scale in question, stage 1 signifies very poor lightstability and stage 8 very high light stability.

The invention will be illustrated but not limited by the followingexamples.

EXAMPLES

I.no.=iodine number, AS=active substance, mins.=minutes, h.=hours.

Unless otherwise stated, "%" means "% by weight" while "g/l" means "g/lliquor".

EXAMPLE 1

700 g tallow (I.no. 52) were mixed with 400 g C₁₆ -C₁₈ fatty acidmethylester (I.no. 80). The resulting mixture was oxidized at 90° C. bypassing air through, and was then sulfited at 95° C. with 1.5 molessodium hydrogen sulfite per kg fat mixture used in the form of anaqueous 40% by weight sodium hydrogen sulfite solution. On completion ofsulfitation, the product was cooled to room temperature.

EXAMPLE 2

500 g palm kernel oil (I.no. 17) were mixed with 500 g C₁₆ -C₁₈ fattyacid methylester (I.no. 80), oxidized at 110° C. by passing air throughand then sulfited at 95° C. with a mixture containing 1.2 moles sodiumhydrogen sulfite and 0.6 moles sodium sulfite/kg fat mixture used in theform of a saturated aqueous solution. On completion of sulfitation, theproduct was cooled to room temperature.

EXAMPLE 3

700 g filtered lard (I.no. 87) were mixed with 300 g C₁₂ -C₁₈ fatty acidmethyleser (I.no. 78), oxidized at 85° C. by passing air through andthen sulfited at 90° C. with 1.3 moles sodium hydrogen sulfite/kg fatmixture used in the form of an aqueous, 40% by weight sodium hydrogensulfite solution. On completion of sulfitation, the product was cooledto room temperature.

EXAMPLE 4

A mixture of 550 g triolein (I.no. 92) and 450 g C₁₆ -C₁₈ fatty acidmethylester (I.no.88) was subjected to oxidizing sulfitation in the sameway as in Example 1.

EXAMPLE 5

A mixture of 500 g technical oleic acid (I.no. 85) and 500 g C₁₆ -C₁₈fatty acid isopropylester (I.no. 80) was subjected to oxidizingsulfitation in the same way as in Example 2.

EXAMPLE 6

600 g technical oleyloleate (I.no. 91) were mixed with 400 g C₁₆ -C₁₈fatty acid methylester (I.no. 85). oxidized at 120° C. by passing airthrough and then sulfited at 90° C. with 2.0 moles sodium hydrogensulfite/kg fat mixture used in the form of an aqueous, 40% by weightsodium hydrogen sulfite solution. On completion of sulfitation, theproduct was cooled to room temperature.

EXAMPLE 7

A mixture of 700 g neat's-foot oil (I.no. 85) and 300 g C₁₆ -C₁₈ fattyacid methylester (I.no. 80) was subjected to oxidizing sulfitation inthe same as in Example 2.

EXAMPLE 8

Chrome-taned leathers were oiled with 7% by weight AS, based on sharingweight, of the sulfited fat mixtures of Examples 1 to 7 and withsulfited fish oil prepared from fish oil (I.no. 135) by oxidation withair at 90° C. and sulfitation at 95° C. with 1.5 moles sodium hydrogensulfite/kg fish oil in the form of an aqueous, 40% by weight sodiumhydrogen sulfite solution. After finishing in the usual way, theleathers are tested for their fastness to light in accordance with DIN54 004. The higher the light stability of the oiling agents, the higherthe stage number on the 8-stage cotton blue scale. Table 1 shows theresults of the individual measurements.

                  TABLE 1                                                         ______________________________________                                                       Fastness to light (as measured in                              Oiling agent   accordance with DIN 54 004)                                    ______________________________________                                        Example 1                      stage 5                                        Example 2                      stage 5                                        Example 3                                                                     Example 4                                                                     Example 5                      stage 4                                        Example 6                                                                     Example 7                                                                     Sulfited fish oil              stage 1                                        ______________________________________                                    

APPLICATION EXAMPLE A

Use during chrome tanning.

All quantities based on pelt weight.

Starting Material: pelts of South-German origin.

    ______________________________________                                        Pickling:                                                                            100%    water 25° C.                                                   8%      sodium chloride       10 mins.                                        0.6%    formic acid (85%)     15 mins.                                                diluted 1:10                                                          0.7%    sulfuric acid (98%)    3 h.                                                   diluted 1:10                                                                  pH ca. 3.5                                                     Tanning                                                                              2%      AS containing                                                  and            95 parts by weight sulfitate.                                  oiling:        prepared from                                                                 60% lard,                                                                     I.no. 80 and                                                                  40%C.sub.12 -C.sub.24 fatty acid                                                                    30 mins.                                                methylester,                                                                  I.no. 85 and                                                                  5 parts by weight                                                             C.sub.16 -C.sub.18 fatty alcohol                                              polyglycolether                                                       8%      commerical chrome     30 mins.                                                tanning agent containing                                                      25% Cr.sub.2 O.sub.3,                                                         33% basic                                                                     basification with                                                             0.5% MgO               7 h.                                                   pH 3.7-3.8                                                                    sharing, retanning,                                                           reoiling in the usual way.                                     ______________________________________                                    

APPLICATION EXAMPLE B

Oiling of upper leathers.

All quantities based on sharing weight.

Starting material: hide wet blue, sharing thickness, 1.7 mm.

    ______________________________________                                        Washing:                                                                              200%    water 40° C.   10 mins.                                                fresh liquor                                                  Neutral-                                                                              100%    water 40° C.                                           ization                                                                               0.5%    sodium formate        30 mins.                                                Rinsing with water at 60° C.                           Retanning                                                                             100%    water 60° C.                                                   0.5%    commercial neutralizing                                                                             15 mins.                                                tanning agent                                                         4%      commercial resin tanning                                                                            30 mins.                                                agent                                                                 3%      commercial synthetic  40 mins.                                                full tanning agent                                            Oiling: 3%      AS sulfitate                                                                  prepared from                                                                 50% triolein,                                                                 I.no. 86 and                                                                  50% fatty acid        45 mins.                                                isopropylester, I.no. 80                                              3%      AS commercial fish oil                                                        sulfate                                                               0.5%    AS C.sub.16 -C.sub.18 alkyl sulfate                                   0.5%    formic acid (85%)     15 mins.                                                diluted 1:10                                                                  hoard up leather and                                                          finish in the usual way.                                      ______________________________________                                    

APPLICATION EXAMPLE C

Oiling of apparel leather.

All quantities based on sharing weight.

Starting material: hide wet blue, sharing thickness 0.8 mm.

    ______________________________________                                        Washing:                                                                              200%    water 40° C.   10 mins.                                                fresh liquor                                                  Chrome  100%    water 40° C.                                           retanning:                                                                            3%      commercial chrome                                                             tanning agent                                                                 containing 25% Cr.sub.2 O.sub.3,                                                                    15 mins.                                                33% basic                                                             3%      commercial synthetic                                                          full tanning agent                                                    1.5%    sodium aluminium silicate                                     Oiling: 3%      AS sulfitate,                                                                 prepared from                                                                 45% lard,                                                                     I.no. 85,                                                                     45% fatty acid methylester,                                                   I.no. 80,             45 mins.                                                10% glycerol monooleate,                                                      I. no. 75,                                                            0.2%    AS tallow alcohol poly-                                                       glycolether                                                           1%      AS C.sub.12 -C.sub.18 alkylsulfate                            Neutral-                                                                              2%      sodium hydrogen carbonate                                                                           60 mins.                                ization:        rinsing 60° C.                                                         dyeing, retanning, reoiling                                                   and finishing in the                                                          usual way.                                                    ______________________________________                                    

APPLICATION EXAMPLE D

Oiling of sheepskin suede.

Starting material: pickled sheepskins

Liquor ratio: 1:20

Chrome tanning: bath temperature 35° C.

    ______________________________________                                        Tanning 40 g/l  sodium chloride                                               and oiling:                                                                           0.5 g/l AS C.sub.12 -C.sub.18 alkyl sulfate                                   4 g/l   As sulfitate, prepared from                                                   60% technical oleyloleate,                                                    I.no. 84,             30 mins.                                                40% C.sub.12 -C.sub.24 fatty acid                                             methylester, I.no. 72                                                 0.5 g/l AS C.sub.16 -C.sub.18 fatty alcohol                                           polyglycolether                                                       4 g/l   commercial chrome tanning                                                                           30 mins.                                                agent containing 25% Cr.sub.3 O.sub.3,                                        33% basic                                                             4 g/l   commercial chrome tanning                                                                           30 mins.                                                agent                                                                 4 g/l   commercial chrome tanning                                                                            5 h.                                                   agent                                                                         move liquor back and forth                                            1 g/l   sodium hydrogen carbonate                                                                           overnight                                       1 g/l   sodium hydrogen carbonate                                                                            4 h.                                                   pH 3.8-3.9                                                                    then hoard up leather and                                                     finish in the usual way.                                      ______________________________________                                    

We claim:
 1. A process for the sulfitation of fats having iodine numbersbelow about 100 comprising the steps of(a) mixing together(i) at leastone fat having an iodine number below about 100, and (ii) at least onefatty acid ester having an iodine number of from about 60 to about 100,containing from 12 to 24 carbon atoms in a linear or branched, naturalor synthetic fatty acid residue, and wherein the ester residue is from amonofunctional C₁ -C₅ alcohol, and wherein the ratio by weight of (i) to(ii) is from about 9:1 to about 1:4: (b) oxidizing the above mixture ata temperature in the range of from about 70° to about 200° C. and (c)reacting the oxidized mixture at a temperature in the range of fromabout 70° to about 110° C. with one or more of an alkali metal hydrogensulfite, an ammonium hydrogen sulfite, an alkali metal sulfite, orammonium sulfite.
 2. A process according to claim 1 wherein step (c) iscarried out in the presence of an oxygen-containing gas.
 3. A processaccording to claim 1 wherein the step (c) from about 0.5 to about 2.5moles of sulfite are employed per Kg of fat mixture.
 4. A processaccording to claim 1 wherein in step (a) the ratio by weight of (i) to(ii) is from about 4:1 to about 2:3.
 5. A process according to claim 1wherein the at least one fat in step (a)(i) has an iodine number of fromabout 7 to about
 95. 6. A process according to claim 1 wherein in step(a)(i) the at least one fat is selected from the group: coconut oil,palm kernel oil, palm oil, tallow, lard, neat's-foot oil, sperm oil,whale oil, triolein, oleic acid, wax esters, fatty acid monoglycerides,fatty acid diglycerides, and fatty acid triglycerides.
 7. A processaccording to claim 1 wherein in step (a)(ii) the at least one fatty acidester has an iodine number of from about 70 to about
 85. 8. A processaccording to claim 1 wherein in step (a)(ii) the at least one fatty acidester contains from 12 to 18 carbon atoms in the fatty acid residue. 9.A process according to claim 1 wherein in step (a)(ii) the at least onefatty acid ester contains from 16 to 18 carbon atoms in the fatty acidresidue.
 10. A process according to claim 1 wherein in step (a)(ii) theester is a methyl, ethyl, isopropyl, or isobutyl ester.
 11. An oxidizedsulfited fat mixture comprisingA. at least one sulfited fat having aniodine number before sulfitation below about 100; and B. at least onesulfited fatty acid ester having an iodine number before sulfitation offrom about 60 to about 100, and containing from 12 to 24 carbon atoms ina linear or branched, natural or synthetic fatty acid residue, andwherein the ester residue is from a monofunctional C₁ -C₅alcohol;wherein the ratio by weight of A to B is from about 9:1 to about1:4.
 12. A mixture according to claim 11 wherein the ratio of A to B isfrom about 4:1 to about 2:3.
 13. A mixture according to claim 11 whereinin component A the iodine number before sulfitation is from about 7 toabout
 95. 14. A mixture according to claim 11 wherein component A is atleast one sulfited fat selected from the group: coconut oil, palm kerneloil, palm oil, tallow, lard, neat's-foot oil, sperm oil, whale oil,triolein, oleic acid, wax esters, fatty acid monoglycerides, fatty aciddiglycerides, and fatty acid triglycerides.
 15. A mixture according toclaim 11 wherein in component B the iodine number before sulfitation isfrom about 70 to about
 85. 16. A mixture according to claim 11 whereinin component B the fatty acid residue contains from 12 to 18 carbonatoms.
 17. A mixture according to claim 16 wherein the fatty acidresidue contains from 16 to 18 carbon atoms.
 18. A mixture according toclaim 11 wherein in component B the ester is a methyl, ethyl, isopropyl,or isobutyl ester.